The present invention relates to a power conversion circuit for converting alternating current power to regulated direct current power and, in particular, to a power factor correction circuit with an integral bridge function providing reduced power consumption.
All electrical and electronic devices and systems require a source of electrical power and, with the exception of devices such as motors that are specifically designed to operate with alternating current power, most devices and systems typically require direct current power at one or more voltage/current levels. In contrast to power requirements of the majority of devices and systems, however, power sources providing alternating current power are typically preferred as being more efficient power generators and as providing higher levels of power and because alternating current power is more easily distributed and more easily converted to different voltage/current levels. Even systems employing direct current power sources, such as batteries, solar cells and fuel cells, therefore typically include direct current to alternating current converters to allow the subsequent generation and distribution of direct current power at various voltage and current levels in the system.
The conversion of alternating current (ac) power from various sources, such as generators, direct current to alternating current (dc-ac) converters, or an electrical power grid, such as the 60 Hz, 117 VAC grid that is standard in the United States or the equivalent power grids of other countries, to direct current (dc) power at various voltage and current levels is therefore a common requirement and problem in a wide range of systems, including computer systems and in the sub-systems of computer systems. A recurring problem with such ac-dc converters, however, is in controlling and minimizing the power losses inherent in such conversions to thereby both deliver more power more efficiently to a system or device using the dc power and to reduce the heat resulting from power losses which must be dissipated or otherwise disposed of. As will be described further in the following description of the invention, this problem is compounded in that a conventional ac-dc converter typically generates regulated dc power from ac power in two stages, each of which results in power losses, the first being the conversion of ac power to unregulated dc power and the second being the regulation of the dc power to provide the desired dc power to a system or device.
The present invention provides a solution to these and other problems of the prior art.
The present invention is directed to a power conversion circuit for converting alternating current power to regulated direct current power and, in particular, to a power factor correction circuit with an integral bridge function providing reduced power consumption.
According to the present invention, a switching power conversion circuit provides direct current power to a load from an alternating current power source by providing current to an energy storage capacitor connected across the load from each of a first switching boost converter circuit and a second switching boost converter circuit operating alternately during corresponding polarity half cycles of the alternating current power source. The first and second switching boost converter circuits each include alternating current inputs connected inversely with respect to each other to first and second terminals of an alternating current power source and current outputs connected in parallel across an energy storage capacitor for storing current from the first and second boost converter circuits and providing direct current power to a load. A gate switching signal is generated to control the switching of the first and second boost converter circuits, and thereby to control the current delivered into the energy storage capacitor and the voltage provided to the load.
The input terminal of the first boost converter circuit and the input return terminal of the second boost converter circuit are connected together for connection to a first terminal of the alternating current power source, and the input terminal of the second boost converter circuit and the input return terminal of the first boost converter circuit are connected together for connection to a second terminal of the alternating current power source. The output terminals of the first and second boost converter circuits are in turn connected to a first end of the energy storage capacitor and output return terminals of the first and second boost converter circuits are connected to a second end of the energy storage capacitor.
According to the present invention, each boost converter circuit includes a switching device having an input and an output connected to a conductive path through the switching path and a switching control input and an inductor having a first end connected from the input terminal of the boost converter circuit and a second end connected to the input of the switching device conductive path. The input of the switching device conductive path is connected to a first end of the energy storage capacitor while the output of the switching device conductive path is connected to a second end of the energy storage capacitor and to the input return terminal of the boost converter circuit and the switching control input of the switching device is connected to the gate switching signal.
The current return path of the first boost converter includes a diode connected between the output and input of the second switching device conductive path, and the inductor connected between the input of the second switching device conductive path and the input terminal of the second boost converter circuit. The current return path of the second boost converter in turn includes a diode connected between the output and input of the first switching device conductive path, and the inductor connected between the input of the first switching device conductive path and the input terminal of the first boost converter circuit.